Fluid-operated lift



Feb. 8, 1944. w. J, MAYTHAM, JR

FLUID-OPERATED LIFT Filed April 2o, 1945 'r l l Q IIIHI Patented F eb. 8, 1944 UNITED STATES PATENT OFFICE 2,341,463 FLUID-OPERATED LIFT Walter J. Maytham, Jr., Wilmette, Ill. Application April zo, 194s, serial No. 483,765

14 Claims.

structures that are of such nature that a passenger elevator structure cannot conveniently or practically be embodied therein. More particularly the invention is intended to be utilized in connection with stairways in buildings, such as residences, apartments, hotels, hospitals and various institutions. It is especially suitable for use in buildings when it is necessary or desirable for the convenience of certain occupants or patients whose physical condition is such as to preclude their climbing of stairs. It will be recognized that in many buildings, and particularly in residences, it is not usually practical to install a conventional passenger elevator, due to room sizes and arrangements in the building. Moreover the matter of cost is an important factor, in addition to the dinculty which would be encountered in providing suitable elevator at the different floors of the building or residence.

One of the objects of the present invention is to provide a novel stair elevator structure which lends itself to practical embodiment in a stairway in residences and other buildings and by ue of which a passenger may be conveniently elevated from one floor to another by merely taking a series of short forward Steps.

Another object is to provide a novel stair elevator of the character indicated wherein individual uid operated lifts are associated with each step of a conventional stairway and wherein each of the lifts are automatically operated in response to the weight of the passenger.

A further object is to provide a novel stair elevator characterized by the provision of separate uid operated lifts, and wherein the lifts are rendered automatically operable in response to the weight of a passenger thereon, to dispose the supporting platform of the lift at a level snbstantially in horizontal alignment with the horizontal upper surface cf the next adjacent upper step. of the stair.

Still another object is to provide a novel stair openings to the elevator of the character indicated which is simple in construction, efficient in operation and `economical to manufacture and install in a conventional stairway structure of a residence or other building. Y

Other objects and advantages of this invention will be apparent from the following description taken in connection with the accompanying drawing,` in` which Figure 1 is a fragmentary, diagrammatic, side elevational view of a portion of a stair provided with fluid lifts embodying the present invention.

Figure 2 is a vertical section through the steps Figure 3 is a vertical sectional view through a portion of the control mechanism of the lift, taken substantially as indicated at line 3 3 0n Figure 2.

Figure 4 is a fragmentary vertical sectional view of a portion of the lift and control mechanisrn, with the control mechanism in an actuated position, preparatory to operating the lift.

Figure 5 is a fragmentary vertical sectional view through the lift and control mechanism of a modied form.

It is to be understood that the lift devices embodying the present invention may be of a type for operation as a pneumatic lift from a source of compressed air, or may be operated as a hydraulic lift by a source of liquid under pressure I have herein shown and described a construction of lift adapted to be operated by compressed air.

posed risers l2. Disposed beneath each step is a uid operated lift indicated generally at i4, and the lift associated with the respective steps are connected in series relation by a single conduit I5, to a. source of compressed air, which may be located at some convenient place in the building.

Each lift device includes an upright cylinder i6 closed. at its upper end by a head l1, which is threaded on the exterior of the cylinder.

standing bracket 2li adapted to seat against the underside of the rearward portion of the step H. The flange t9 and bracket 20 are adapted t0 "and 3S.

be connected rigidly to the riser and step respectively by bolts 2l. The step Il, immediately above the cylinder, is provided with an elongated rectangular opening 23 in which is normally seated a platform or tread 24, which preferably is of a size to conveniently support a person thereon.

The platform is rigidly secured to a flanged fitting 26, which in turn is rigidly connected to the upper end of a piston rod 21, the lower end of the piston rod being connected toa piston 28, snugly fitting and normally disposed at the lower end of the cylinder, as seen in Figure 2 of the drawing. The piston rod is guided at its upper end in a bearing 35 formed as an integral part of the head l1'. When the piston 28 is moved upwardlythe platform 24 moves therewith as a unit, and it s to be understood that the stroke of the pistonr is such that the platform in its elevated position will be disposed substantially ush with the horizontal upper surface of the next upper step l i of the stairway, as seen in Figure 1 of the drawing, and when disposed in its lowered position, it is substantially as seen in Figure 2 of the drawing, with the supporting surface thereof disposed just slightly above the upper surface of the step Il. The amount that the supporting surface of the platform projects above the step need only be a small fraction of an inch so as to permit depression of the platform and the cylinder by the weight of a person thereon, to initiate the operation of control mechanism to be presently described.

To preclude rotation or turning of the platform or tread 24, about the axis of the cylinder, so Vas to always insure that the platform will telescope into registration with the opening 23 of thestep, I provide suitable guide means for the piston rod. For this purpose the piston rod is provided with a pair of diametrically opposite, longitudinally extending grooves 32, into which project or extend the terminal end portions Yof screws 34 carried in the bearing 30. It will be noted that the upper end of the grooves terminate substantially flush with the upper end of the bearing 30 in the normal inoperative position of the lift, and when the platform and piston commence to move vertically,

the air in the cylinder-above the piston. The relationship of the upper ends of the groovesto the bearing 30 is such that in the normal inoperative or lowered position of the platform and piston, the grooves are substantially closed so as to preclude the entrance of dust or dirt, or other foreign matter, within the chamber of the cylinder.

. The lower end of the cylinder l is closed by a bottom member 3B, in the form of a casting, to which is connected at one end a casting 31, which castings together serve to enclose suitable con- `trol mechanism. The casting 36 is threaded'onto the exterior of the lower end of the cylinder, and

of .the ducts opening into a cylindrical bore or chamber 45 provided in the cast bottom member'36. v

Slidably guided in the bore 4l] is a main control valve 4l, provided with axially spaced-apart, peripheral grooves 42 and 43, adapted to be selectively registered with the respective ducts 38 The lower side of the bore 4() is prothe grooves 32,4 serve as atmospheric vents to perm`t escape of the inner Wall of the cylinder I6, v

vided with a port which provides communication between the bore 40 and a fluid supply duct 46, which terminates at opposite ends in pilot valve chambers 41 and 48 in the castings 36 and 31, respectively. The bore 40 is provided with a laterally extending port 49, located in spaced-apart vertical alignment with the outlet duct 39, and serves to provide for the discharge of the compressed air in the cylinder below piston 23, to atmosphere when the main valve 4| is moved to the position seen in Figure 2 of the drawing, with its peripheral groove 43 disposed `in registration with the outlet duct 39 and the port 49.

The opposite ends of the chamber 40 are provided with atmospheric vents 5l and 52 so as to permit the main valve 4I to be freely moved axially within the bore 40 as will hereafter be described.

In the pilot valve chamber 41 is a valve port 54 which provides communication between lthe chamber 41 and the right hand end of the bore 4i). The valve port 54 is controlled rby a valve 55, which is normally urged to closed position by a coil spring 55. Connected to the upper end of the valve 55 is an operating member 58, which projects through the .bottom casting 36 and extends a short distance upwardly into the bottom of the chamber of the cylinder I6, in position to be engaged by the bottom of the piston 28. It is to be understood that the spring 56 is of sufficient tension as to normally maintain the valve 55 seated, and in addition, through the operating member 58, serves to supporty the piston 2S together with the rod 21, and platform 24 in the position seen in Figure 2 of the draw'- ing.

The pilot valve chamber 48 is provided with a port E0 which provides communication between the chamber 4B and the left-hand end of the bore 40 of the control mechanism. The port 6D is normally closed by a valve element 6| to which is connected the lower end of an operatingI rod 6?.. The upper end of said rod is guided in an aperture in a flange of the cylinder head I1,

and terminates in position to abut against one end of a lever 63, which is pivoted at E4 on the bracket 25, The opposite end of the lever 63 normally abuts against a headed control button 5%, projecting downwardly through the top of the cylinder head I1, with the stern portion extending a short distance below said head, into the chamber of the cylinder IB, in position to be engaged by the head of the piston 28. The pilot valve 6| is normally held closed and thelever 53 and connecting rod 62 are normally held in the position seen in Figure 2 of the drawing by means of a coil spring 68.

`li'he end casting 31 is provided with a threaded opening 19, communicating with pilot valve chamber 48, and serving to receive a T-shaped fitting 1l, the ends of which fitting are connected to the pipes I5, to a source of compressed air, so that the source of compressed air is at all times admitted into the duct 46, and pilot valve chambers 41 and 48, available for actuating the main valve 4|, incident to operation of either of the pilot valves 55 or 6l.

Operation mi'tting compressed air through the port react aga-inst 'the end of the mai-n valve 40, to move the latter from the position seen in Figure A2 t'o the `position seen in Figure 4 of the ydrawing'. Ther air normally within the left-hand end of the bore lill, prior to suc-h movement of the main valve, is discharged to atmosphere through the vent 52. When this adjustment of the main valve 4l takes pla-ce, the compressed air is then admitted through the port 45 into the registered peripheral groove 46, and into the inlet duct 38, and the bottom of the cylinder l5, below piston 28, causing the platform 24, with the person thereon, to move in an upwardly direction. Im-

mediately after such upward vmovement takes f' place, the operating member 53 is disengaged so that the pilot valve '55 is again closed.

When the platform 24 approaches a position, substantially flush with the upper horizontal surface of the next upper step, as seen in Figure 1 of the drawing, the upper surface of the piston 23 engages the lower end of the button 66, and moves the lever 53, so as to depress the rod G2 to cause opening of the pilot valve BI, at which time compressed air is admitted through the port 60, to react on the left-hand end of the main valve 4i, and move the latter from the position seen in Figure 4 to the position seen in Figure l of the drawing, and the air at the righthand end of the main valve 4| is permitted to discharge freely to atmosphere through the vent opening 5l. When the main valve moves to the position seen in Figure 2, the source of compressed air supplied through the inlet duct 38 is shut off, and the outlet duct 39 has registered therewith the peripheral groove 43 of the valve element li i, which groove is also in turn in registration with the atmospheric duct 49, so that the compressed air within the cylinder iii, beneath the piston 25, is `permitted to discharge to atmosphere and the piston 28, rod 2l and platform 275 are permitted to move downwardly to the position seen in 'Figure 2 of the drawing, at which position the cycle of operation may be repeated.

The speed of raising and lowering of the platform "2d, together with the piston 28, may be varied by adjustment of valve members 12 as seen in Figure 3 of the drawing, which serve to vary the effective cross-sectional area of the inlet and outlet ducts 38 and 39.

In the modified construction shown in Figure 5 of the drawing, the control mechanism vis located substantially at the side of the main cylinder Ia in order to reduce to a minimum the overall height of the lift device. In this construction the control mechanism includes a housing member 6l) suitably connected to a laterally extending cast portion 8| which is formed integrally with the cylinder bottom a. The extension portion 8l and bottom 38a are formed with a single combination inlet and outlet duct 82 in which there is disposed an inlet ball check valve B3 and an outlet ball check valve 84, which valves are arranged in opposite relation for controlling, respectively, the inlet flow and outlet flow of the air through the duct 82. One end of the duct 82, as may be clearly seen in Figure 5 of the drawing, opens into the lower end of the chamber of the cylinder Mia, beneath the piston 28a, and the opposite end of the duct opens into a chamber 85 of the housing Si), in which there is mounted a dual valve arrangement including pilot valves 86 and 8l disposed in opposed relation to each other for controlling, respectively, ports 88 and 89 at opposite ends of the chamber 85.

lcommunicates with a the lever cooperates with The stem portion which connects the dual valves .86 and 81 is provided with an annular shoulder 9E, having oppositely beveled faces with which cooperate a pair of spring-pressed ball detents 92. These detents tend to cause movement of the dual valve elements with a snap action and serve to yieldingly maintain said pilot valve elements at either of their two positions of adjustment, namely, with the valve 86 seated and the valve 81 in open position, or with the Valve 81 seated and the valve 86 in open position. The lower end of the chamber through port 88 duct 94, the outer end of which duct is threaded for receiving a pipe fitting 1|, connected in series with the pipes I5, to a source of compressed air supply. The upper end of the valve 81 is formed with an upstanding lug 87a to which is connected the lower end of a spring connecting rod 97. The upper end of the rod is connected to a lever 133m, pivoted at 64a on the bracket 26a. The opposite end of an operating button 66a slidably seated in the upper end of the head lla of the cylinder.

Vertically movable in a boss Sil formed integrally with the bracket 20c is a headed plunger 99 around which is disposed reacting between the head of the plunger and the boss 9B, and with the head of the plunger positioned to be engaged by the underside of the platform 24a.

Operation Normally the platform 24a is in the position indicated in dotted lines in Figure 5, which woul be the same as the position seen in Figure 2 of the drawing, When the weight of a person is imposed on the platform, it is depressed to the position seen in full lines in Figure 5 of the drawing, and which, through the plunger 59, moves the lever 63a, and through the connecting rod 91 moves the dual pilot valves to the position seen in Figure 5 of the drawing. At this position of adjustment the compres-sed air is admitted through the duct Si@ into the chamber 35, and thence through the duct 82 into the bottom of the chamber of the cylinder l'a, to cause the piston 20a, together with the platform 24a to be raised, together with the person thereon, to a position as indicated diagrammatically in Figure l ofthe drawing.

When the piston approaches its upper limit of movement, it engages the lower end of the button 56a and operates the lever lilla in opposite direction, which in turn, through the spring connecting rod Sl, shifts the dual pilot valve downwardly to seat the pilot valve S6, cutting off the supply of compressed air, and opening the pilot valve 37 so as to vent the cylinder ld beneath the piston 28a, to atmosphere, and the compressed air therein is permitted to discharge through the duct 82, chamber 85, and through the pilot valve port 33. As the. compressed air in cylinder ita is discharged, the platform Ma is-caused to move downwardly to the position seen in dot-ted lines in Figure 5.

When the platform and its piston arrive at its lower position of adjustment, the control mechanis-m is in condition ready to repeat the cycle of operation. In this connection it is to be understood that the coil spring itil is of sufficient tension to resiliently support the weight of the platform 24a together with the connecting rod 2M and piston 23a in proper position so that the platform in response to the weight of a person vtally disposed,

'vating units associated thereon, may be initially depressed a small amount, as above stated, from the dotted position to the full line position, for adjusting the control mechanism and kinitiating operation of the lift.

When a lift is to be mounted in the floor, 'immediately in front of the first step of the stair, the supporting bracket for the lift may be slightly modified to insure proper anchorage in position. If the iioor is concrete or other material than wood, it may be necessary to provide suitable cavities therein for accommodating the liftassociated with the rst step, and also the lift in the iloor in front of the first step.

It is to be understood that the platform may be formed of substantial size, with the eective supporting area positioned to overlie the step proper. Furthermore the aligned projecting edge portion of the next adjacent upper step may be cut away to insure adequate clearance for the feet of the person when the lift is in operation, and which also permit the use of a platform of greater width.

Although I have herein shown and described certain embodiments of my invention, it is to be understood to be illustrative only, as it is capable of modification and rearrangement of parts without departing from the spirit and scope thereof. I do not, therefore, wish to be understood as limiting this invention to the precise form herein disclosed, except as I may be so limited by the appended claims.

I claim as my invention:

l. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizonvertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston mounted in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere and the lower end being provided with inlet and outlet duct means, control means including valve means in the inlet duct for controlling communication of the cylinder, below the piston, with a source of compressed air, and valve means in the outlet duct for controlling venting of the bottom of the cylinder, below the piston, to atmosphere, and means actuated in response to pressure on the platform for operating said control means for causing opening of the valve means in the inlet duct and closing of the valve means in the outlet duct, whereby compressed air is supplied to the cylinder for raising said piston and platform for disposing the latter in substantially horizontal alignment with the adjacent upper step of the stair.

2. A stair elevator comprising individual elewith each step of the stairs, each elevating unit comprising a horizontally disposed, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston mounted in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere and the lower end being provided with inlet and outlet duct means, control means including valve vertically movable platform,A

means in the inlet duct for controlling communication of the cylinder, below the piston, with a source of compressed air, and valve means in the outlet duct for controlling venting of the bottom of the cylinder, below the piston, to atmosphere, sure on the platform for operating said control means for causing opening of the valve means in the inlet duct and closing of the valve means in the outlet duct, whereby compressed air is supplied to the cylinder for raising said piston and platform for disposing the latter is substantially horizontal alignment with the adjacent upper step of the stair, and means engageable by the piston as the platform approaches such aligned position for actuating the control for causing closure of the valve means in the inlet duct and opening of the valve means in the outlet duct, and permitting said piston and platform to move downwardly to their lowered position of adjustment under control of the discharge of the compressed air in the cylinder to atmosphere.

3. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston mounted in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere and the lower end being provided with inlet and outlet duct means, control means including valve means in the inlet duct for controlling communication of the cylinder, below the piston, with a source of lcompressed air, and valve means in the outlet duct for controlling venting of the bottom of the cylinder, below the piston, to atmosphere, means actuated in response to pressure on the platform for operating said control means for causing opening of the valve means in the inlet duct and closing of the valve means in the outlet duct, whereby compressed air is supplied to the cylinder for raising said piston and platform for disposing the latter in substantially horzontal alignment with the adjacent upper step of the stair, and means associated with said actuating means for resiliently supporting said piston and platform in their lowered position of adjustment.

4. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston mounted in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere and the lower end being provided with inlet and outlet duct means, control means including valve means in the inlet duct for controlling communication of the cylinder, below the piston, with a source of compressed air, and valve means in the outlet duct for controlling venting of the bottom of the cylinder, below the piston, to atmosphere, means actuated in response to pressure on the platform for operating said control means for causing opening of the Lvalve means in the inmeans actuated in response to preslet duct `and closing of the valve means in the outlet duct, whereby compressed air is Supplied to the cylinder for raising said piston and platform for disposing the latter in substantially horizontal alignment vwith the adjacent upper step of the stair, means engageable by the piston as the platform approaches such aligned position for actuating the control for causing closure of the valve means in the inlet duct and opening of the valve means in the outlet duct, vand permitting said piston and platform to move downwardly to their lowered position of adjustment under control of the discharge of the compressed air in the cylinder to atmsophere, and means associated with each of said inlet and outlet ducts for varying the flow of compressed air therethrough to vary the rate of speed of raising and lowering respectively of said piston and platform.

5. A stair elevator comprising individual eleating units associated with each step of the a piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved ver tically as a unit, the upper end of the cylinder being vented to atmosphere and the lower end being provided with inlet and outlet duct means, a master valve for controlling communication of the inlet duct with a source of compressed air and controlling venting of the outlet duct to atmosphere, said master valve being connected by duct means to the source of compressed air and operable `thereby for controlling said inlet and outlet ducts, a normally closed pilot valve in said duct means to the master valve, and an operating member connected to said piston as it approaches its lower position of adjustment, whereby vpressure on the platform moves the piston downwardly a small amount and moves the operating member to effect temporary opening of the pilot valve for moving the master valve and causing closure of the said outlet duct means and opening of the inlet duct means for admitting compressed air below the piston to elevate said piston and platform to dis,

pose the latter substantially flush with the upper surface of the adjacent upper step.

6. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically. movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step,

`a piston in the cylinderand having an upwardly by duct -means to the source of compressed air and operable Vthereby for vcontrolling said inlet and outlet ducts, a normally closed pilot Valve in said duct means to the master Valve, .an

,70 atmosphere, said master valve being connected 5 operating member connected to said pilot Valve and having a portion extending up through the bottom of the cylinder in position to'engage said piston as `it approaches its lower position ofadjustment, and spring means serving to hold Vthe pilot valve closed land for yieldingly supporting the piston and platform at their lowered position of adjustment, whereby pressure `on the platform moves the pist-on downwardly a small amount andmoves the operating Vmember to effect temporary opening of the pilot valve for moving the master valve and causing closure of the .said outlet duct mean-s and opening of the inlet duct 'means for admitting compressed air below thepiston to elevate said piston and platform .to dispose the latter substantially flush Vwi-th the upper surface of the adjacent upper step.

l7. A stair elevator comprising individual eleassociated with each step Aof the an upright Vcylinder adapted to be connected to the underside of the stair beneath the said step, a piston 4in the cylinder and having an upwardly projecting piston rod operably connected at its 'upper end to said platform, whereby said piston and platform are adapted to be moved vertically provided vwith inlet and outlet duct means,4 a master valve for controlling communication of the inlet duct with a source of compressed air and controlling venting of the outlet duct to atmosphere, said master valve being connected :by duct `means to the source of compressed air and operable thereby for controlling said inlet and outlet ducts, a normally closed pilot valve in 1said duct means to the master valve, van operating member rconnected to said pilot valve andhaving a portion extending up through the 'bott-om of 'the cylinder in position lto engage said 'piston as it approaches its lower position of adjustment', whereby pressure onV the platform moves the piston downwardly a small amount and moves the operating member to effect tem'- porary opening of the pilot valve for moving the master valve and causing closure of the said the piston to elevate said piston and platform to dispose the latter substantially flush with vthe upper surface of the adjacent upper step, a normally closed second pilot Valve in said duct means, and operati-ng means connected to said second pilot valve and including a vpart projecting downwardly from the upper end of the cylinder and engageable by said piston as it approaches its upper limit -of movement, for opening said second pilot valve and moving the master valve to a position for closingthe inlet duct and venting the outlet duct to atmosphere fol` permitting the piston and platform to 'lower under control of the compressed air discharged through the outlet duct. y 8. A stair elevator comprisingindividual elevating units Aassociated with each ,step of 'the stairs, each elevating unit ,comprisingza A'hori`- zontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the 'underside of the stair .beneath the said step,

unit, the upper end 6 being vented to atmosphere and the lower end being provided with inlet and outlet duct means, a master valve for controlling communication of the inlet duct with a source of compressed air and controlling venting of the outlet duct to atmosphere, said master valve being connected by duct means to the source of compressed air and operable thereby for controlling said inlet and outlet ducts, a normally closed pilot valve in said duct means to the master valve, an operating member connected to said pilot valve and having a portion extending up through the bottom of the cylinder in position to engage said piston as it approaches its lower position of adjustment, whereby pressure on the platform moves the piston downwardly a small amount and moves the operating member to effect temporary opening of the pilot valve for moving the master valve land causing closure of said outlet duct means and opening of the inlet duct means for admitting compressed air below the piston to elevate said piston and platform to dispose thev latter substantially flush with the upper surface of the adjacent upper step, a normally closed second pilot valve in said duct means, operating means connected to said second pilot valve and including a part projecting downwardly from the upper end of the cylinder and engageable by said piston as it approaches its upper limit of movement, for opening said second pilot valve and moving the master valve to a position for closing the inlet duct and venting the outlet duct to atmosphere for permitting the piston and platform to lower under control of the compressed air discharged through the outlet duct, spring means yieldingly urging the second pilot valve to closed position, and separate spring means yieldingly urging the first-mentioned pilot valve to closed position and acting on the operating member. in amanrner to yieldingly support the piston and platform at a lowered position of adjustment.

9. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the Yunderside of the stair beneath the said step, a piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a of the cylinder being vented to atmosphere, and the lower end being provided with inlet and outlet duct means, a master valve for controlling communiction of the inlet duct with a source of compressed air and controlling venting of the outlet duct to atmosphere, said master valve including a cylindrical chamber with which the inlet and outlet ducts connect, a separate pair of ports connected respectively to the supply of compressed air and to atmosphere, a cylindrical valve plug mounted for axial movement in the chamber and having two sets of ports for selectively vcompleting communication of the inlet duct with the source of compressed air and for connecting the outlet duct to atmosphere, separate ducts for connecting the opposite ends of the valve chamber to the source of compressed air, a pilot valve in one duct including an operating member extending up into the bottom of the cylinder and moved by the piston vwhen downward pressure is exerted on the platthe pilot valve for moving the the outlet duct and open form, for opening master valve to close the inlet duct to admit compressed air below the piston to raise the platform, and a second pilot valve in the other duct at the other end of the valve chamber, and operating means for said second pilot valve including a member projecting downwardly in the upper end of the cylinder and engageable by the piston as it approaches its upper limit of movement for causing opening of said second pilot valve and: thereby moving the master valve to close the inlet vduct and Vopen the outlet duct for venting the piston cylinder to atmosphere and permitting the piston and platform to move downwardly under control of the discharge of compressed air from the piston cylinder.

10. A stair elevator comprising individual elevating `units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an

lupright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere, a master control valve includinga chamber provided at one end with a port in communication with a source of compressed air and a second port for venting to atmosphere, interconnected dual value elements for alternately sealing said ports, a single duct communieating with said chamber and the bottom of the cylinder and adapted to serve as both an inlet and outlet duct, operating means for the dual valve elements including an abutment lever, a depending member on the platform, spring means for yieldingly supporting the platform at its lowered position of adjustment with the depending member in position to engage the lever and adapted to move the lever, when downward pressure is exerted on the platform, to move the dual valve member to open the port to compressed air supply and closing the port for venting to atmosphere, and an abutment member carried in the upper end of the piston cylinder in position to 'register with said lever, and having a part projecting into the cylinder in position to be engaged by the piston as it approaches its upper limit of movement for moving the abutment member to actuate the lever in the opposite direction for reversing the dual valve to cause closing of the port to compressed air supply and opening the port for venting to atmosphere, whereby the air below the piston is discharged to atmosphere to permit the piston and platform to move downwardly to its lower position of adjustment.

11.4 A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a. piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere, a master control valve including a vchamber provided at one end with'a port in communication with a source of compressed air and a second port for venting to atmosphere, interconnected dual valve elements for alternately sealing said ports, a single duct communicating with said chamber and the bottom of the cylinder and adapted to serve as both an inlet and outlet duct, operating means for the dual valve elements including an abutment lever,

a depending member on the platform, spring means for yieldingly supporting the platform at its lowered position of adjustment with the de.- pending member in position to engage the lever and adapted to move the lever, when downward pressure is exerted on the platform, to move the dual valve member to open the port to compressed air supply and closing the port for venting to atmosphere, an abutment member carried in the upper end `of the piston cylinder in position to register with said lever, and having a part projecting into the cylinder in position to be engaged by the piston as it approaches its upper limit of movement for moving the abutment member to actuate the lever in the opposite direction for reversing the dual valve to cause closing of the port to compressed air supply and opening the port for venting to atmosphere, whereby the air below the piston is discharged to atmosphere to permit the piston and platform to move downwardly to its lower position of adjustment, and spring means for yieldingly maintaining the dual valve elements in either of its positions of adjustment.

12. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere, a master control valve including a chamber provided at one end with a port in communication with a source of compressed air and a second port for venting to atmosphere, interconnected dual valve elements for alternately sealing said ports, a single duct communicating with said chamber and the bottom of the cylinder and adapted to serve as both an inlet and outlet duct, operating means for the dual valve elements including an abutment lever, a depending member on the platform, spring means for yieldingly supporting the platfrom at its lowered position of adjustment with the depending member in position to engage the lever and adapted to move the lever, when downward pressure is exerted on the platform, to move the dual valve member to open the port to compressed air supply and closing the port for venting to atmosphere, an abutment member carried in the upper end of the piston cylinder in position to register with said lever and having a part projecting into the cylinder in position to be engaged by the piston as it approaches its upper limit of movement for moving the abutment member to actuate the lever in the opposite direction for reversing the dual valve to cause closing of the port to compressed air supply and opening the port for venting to atmosphere, whereby the air below the piston is discharged to atmosphere to permit the piston and platform to move downwardly to its lower po sition of adjustment, and separate adjustment means associated with said single duct for varying independently of each other the fiow of air into and out of the cylinder for controlling the speed of raising or lowering of the piston and platform.

13. A stair elevator comprising individual elevating units associated with each step of the stairs, each elevating unit comprising a horizontally disposed, vertically movable platform, an upright cylinder adapted to be connected to the underside of the stair beneath the said step, a piston in the cylinder and having an upwardly projecting piston rod operably connected at its upper end to said platform, whereby said piston and platform are adapted to be moved vertically as a unit, the upper end of the cylinder being vented to atmosphere, means for resiliently supporting the piston and platform at their lowered position of adjustment, a'master control valve including a chamber provided at one end with a port in communication with a source of compressed air and a second port for venting to atmosphere, interconnected dual valve elements for alternately sealing said ports, a single duct communicating with said chamber and the bottom of the cylinder and adapted to serve as both an. inlet and outlet duct, operating means for the dual valve elements including an abutment lever, a depending member on the platform, spring means for yieldingly supporting the platform at its lowered position of adjustment with the depending member in position to engage the lever and adapted to move the lever, when downward pressure is exerted on the platform, to move the dual valve member to open the port to compressed air supply and closing the port for venting to atmosphere, and an abutment member carried in the upper end of the piston cylinder in position to register with said lever, and having a part projecting into the cylinder in position to be engaged by the piston as it approaches its upper limit of movement for moving the abutment member to actuate the lever in the opposite direction for reversing the dual valve to cause closing of the port to compressed air supply and opening the port for venting to atmosphere, whereby the air below the piston is discharged to atmosphere to permit the piston and platform to move downwardly to its lower position of adjustment.

14. For use with a conventional stairway including a series of vertically spaced steps, a series of fluid operated lifts, operable by a source of fluid under pressure, one lift being associated with each step and including a horizontally disposed Dlatform, and control means operable in response to the weight of a person on the platform to effect raising of the latter to a position substantially flush with the next adjacent upper step.

WALTER J. MAYTHAM, J R. 

